CkPython

Wait for a Message on Any SSH Channel

Demonstrates the Chilkat Ssh.WaitForChannelMessage method, which waits for the next SSH channel message on any channel. The only argument is the poll timeout: 0 for a nonblocking check, a positive value to wait that long, or a negative value to wait with no method-level timeout. It returns the channel number the message belongs to, -1 if nothing arrived before the timeout, or -2 on another error such as a lost connection.

Background: When several channels are active at once, waiting on one specific channel would block while others sit ready. This method is the multiplexed alternative — it returns as soon as any channel has activity and tells you which one, so a single loop can service them all. The explicit timeout argument governs the wait; shorter ReadTimeoutMs values do not cut it short.

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import sys
import chilkat

success = False

#  Demonstrates the Ssh.WaitForChannelMessage method, which waits for the next SSH channel
#  message on ANY channel.  The only argument is the poll timeout in milliseconds: 0 for a
#  nonblocking check, a positive value to wait that long, or a negative value to wait with no
#  method-level timeout.

ssh = chilkat.CkSsh()

sshPort = 22
success = ssh.Connect("ssh.example.com",sshPort)
if (success == False):
    print(ssh.lastErrorText())
    sys.exit()

#  Normally you would not hard-code the password in source.  You should instead obtain it
#  from an interactive prompt, environment variable, or a secrets vault.
password = "mySshPassword"

success = ssh.AuthenticatePw("mySshLogin",password)
if (success == False):
    print(ssh.lastErrorText())
    sys.exit()

channelNum = ssh.OpenSessionChannel()
if (channelNum < 0):
    print(ssh.lastErrorText())
    sys.exit()

success = ssh.SendReqExec(channelNum,"ls -l /tmp")
if (success == False):
    print(ssh.lastErrorText())
    sys.exit()

#  Wait up to 5 seconds for the next channel message.  The return value is the channel number
#  the message belongs to, -1 if nothing arrived before the timeout, or -2 on another error.
pollTimeoutMs = 5000
result = ssh.WaitForChannelMessage(pollTimeoutMs)

if (result == -2):
    print(ssh.lastErrorText())
    sys.exit()

if (result == -1):
    print("No channel message arrived before the timeout.")

if (result >= 0):
    print("Processed a message for channel " + str(result))

ssh.Disconnect()